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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

CERESINE

163

cold with about 200 c.c. of approximately 95% alcohol; the liquid is filtered,
the alcohol evaporated off and the residue examined. A yellow or brown
colour indicates the probable presence of resin, recognisable by the reactions
given for heavy oils (Chemical Tests, 7) ; a white residue probably consists
of stearic acid. In any case the natuie of the residue may be ascertained
by determining the acid and saponification numbers.

5.  Detection of Carnauba Wax.—This is often added in small pro-
portion to paraffin wax to raise its melting point.    Indications of its presence
are given by the characteristic aromatic odour and by the saponification
number (zero for pure paraffin wax).   When, therefore, the product has a
saponification number, it is tested for carnauba wax, the following method
being employed :   10 grams of the wax, chopped as finely as possible, are
digested for some hours with about 500 c.c. of ether, with frequent shaking.
After filtration, the insoluble residue—in which the carnauba wax is con-
centrated—is washed with ether, pressed between absorbent paper and
left in the air to dry.    The saponification number is then determined and,
in presence of carnauba wax, is markedly higher than that of the original
substance.    In doubtful cases the residue may be again treated with ether,
so as to obtain a residue still richer in carnauba wax.

The melting point of the insoluble residue is also determined, this being
considerably higher than that of the original material if carnauba wax is
present. Finally, the carnauba wax may be identified by decomposing the
soap obtained by means of an acid and determining the melting point of
the separated fatty acids.

6.  Detection of Coal-tar Colours.—Any colour in the paraffin wax
indicates that a coal-tar colour may be present.    To confirm this, the pro-
duct is extracted with alcohol and the solution tested as usual (see Coal-Tar

Colours).

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* *

Refined paraffin wax should be white or only faintly yellow, neutral and free
from suspended impurities, and should not render sulphuric acid appreciably
brown. The melting point varies somewhat: ordinary hard paraffin waxes
usually melt at 50-60°, whilst soft ones melt below 50° and in some cases at 30°.
On the other hand, paraffin wax melting considerably above 60°, like that from
Java, is occasionally found, but in general a product melting below 60° may be
regarded as a paraffin wax, and one melting between 60° and 66° as a mixture
of paraffin wax and ceresine (see later). Such limits are not valid if carnauba
wax is present, 5% of this sufficing to raise the melting point by several degrees.

CERESINE

Ozokerite (crude ceresine) is dark yellow or brown, but ceresine itself
is white or only faintly yellow, opaque and similar in appearance to white
wax. The following tests are made :

1.  Suspended  Impurities.    Reaction.    Behaviour towards  Sul-
phuric Acid.—As in Vaseline (q.v., I, 3 and 4).

2.  Melting and Solidifying Points.—See Paraffin Wax, 2.

3.  Detection and Determination of the Paraffin Wax.—(a] MICRO-ble in alcohol, whilst the artificial ones contain